Hydrocarbons n -octane

To address the primary compositional characteristics of coal-derived type synthetic fuels, a neat aromatic hydrocarbon (toluene) and a neat aliphatic hydrocarbon (n-octane) were selected for this study. 

Fig. 9.1. The chain of carbon atoms in the hydrocarbon, n-octane (C8H18), linked by sp3 bonds, exemplifies the simplest type of organic compounds. This and the succeeding diagrams of molecules are not drawn to scale. They are intended only to show the bonding connexions between the atoms, and some of the spatial relations that those connexions imply.

Fig. Ill-16. Surface tension lowering of water at 15°C due to adsorption of hydrocarbons. , n-pentane A, 2,2,4-trimethylpentane O, n-hexane x, n-heptane A, n-octane. (From Ref. 133.)...

The formation of alkenes and alkene-related polymerization products can seriously reduce the yields of desired alkane products from secondary alcohols, which can undergo elimination reactions. For example, reduction of 2-octanol at 0° with boron trifluoride gas in dichloromethane containing 1.2 equivalents of tri-ethylsilane gives only a 58% yield of n-octane after 75 minutes (Eq. II).129 The remainder of the hydrocarbon mass comprises nonvolatile polymeric material.126... 

As previously mentioned, Davis (8) has shown that in model dehydrocyclization reactions with a dual function catalyst and an n-octane feedstock, isomerization of the hydrocarbon to 2-and 3-methylheptane is faster than the dehydrocyclization reaction. Although competitive isomerization of an alkane feedstock is commonly observed in model studies using monofunctional (Pt) catalysts, some of the alkanes produced can be rationalized as products of the hydrogenolysis of substituted cyclopentanes, which in turn can be formed on platinum surfaces via free radical-like mechanisms. However, the 2- and 3-methylheptane isomers (out of a total of 18 possible C8Hi8 isomers) observed with dual function catalysts are those expected from the rearrangement of n-octane via carbocation intermediates. Such acid-catalyzed isomerizations are widely acknowledged to occur via a protonated cyclopropane structure (25, 28), in this case one derived from the 2-octyl cation, which can then be the precursor... 

Yang et al. [2] have compared sorbent trapping with solvent trapping after the supercritical fluid extraction of volatile petroleum hydrocarbons in soil. Sorbent trapping yielded quantitative collections of n-alkanes as volatile as n-hexane, while solvent trapping effectively collected w-alkanes as volatile as n-octane. 

The API Subcommittee for Technical Data is sponsoring phase equilibria work by Grant Wilson (Wilco Co.) on water non-hydrocarbon/ hydrocarbon systems. The first system will be n-octane, ethylbenzene, and ethyl cyclohexane as binaries with water and as ternaries with hydrogen sulfide as the third component. 

Interaction parameter was also generated for the hydrocarbon -rich phases of the n-octane - water system. The data of Kalafati and Piir (37j were used. There were no data available for the water - rich liquid phase for this binary. 

Experimental solubility data are available for some higher alkane - water systems (see, for example, Skripka et al., (38)). However, these data either cover only a very limited temperature range or contain results for one phase only. No attempt has been made to determine the interaction parameters for water - hydrocarbon systems where the hydrocarbon is larger than n-octane. 

The mean absolute deviations of LDA method are much larger (216.5 kcal/mol vs. 91.9 kcal/mol). The increase in the deviations is largest for the hydrocarbons and their substituted derivatives. For B3LYP, the mean absolute deviations increase from 2.92 kcal/mol (G2/97) to 9.64 kcal/mol (G3-3 subset) for the hydrocarbons, and from 2.22 kcal/mol (G2/97) to 7.15 kcal/mol (G3-3 subset) for substituted hydrocarbons. The B3LYP mean absolute deviation for the non-hydrogen species increases from 5.15 kcal/mol to 10.99 kcal/mol. An example of the increase in error with molecular size is evident from comparison of results for propane and n-octane. The B3LYP enthalpy deviates from experiment by -1.46 kcal/mol for propane and -14.04 kcal/mol for n-octane. The G3 deviations for these cases are only 0.33 kcal/mol and 0.88 kcal/mol, respectively. The error per bond in G3 theory is about 0.035 for both propane and n-octane, whereas for B3LYP it is 0.146 and 0.51 kcal/mol, respectively. 

Aromatization of hydrocarbons with more than six carbon atoms is thermodynamically even more favorable than the reaction of n-hexane 28). These hydrocarbons offer more than one way of cyclization, for example, n-octane may give either o-xylene or ethylbenzene. -Nonane can even give bicyclic products (indane system) (72). 

The activity data confirm that an IR absorption band at 960 cm" is a necessary condition for titanium silicates to be active for the selective oxidation of hydrocarbons with aqueous H2O2 as suggested by Huybrechts et al. (9). However, this band is not a sufficient condition for predicting the activity of the TS-1 catalyst. Although TS-l(B) and TS-l(C) show intensities for the 960 cm- band similar to TS-1 (A), their activities are different First of all, the reaction data reveal that TS-1 (A) is much more active than TS-l(B) for phenol hydroxylation, while both samples show similar activity for n-octane oxidation and 1-hexene epoxidation. Therefore, the presence of the IR band at 960 cm-i in TS-1 catalysts may correlate with the activities for the oxidation of n-octane and the epoxidation of 1-hexene but not for phenol hydroxylation. However, note that the amorphous Ti02-Si02 also has an IR absorption band at 960 cm- and it does not activate either substrate. 

Alhedai et a also examined the effect of exclusion on dead volume measurement. A mobile phase consisting of n-octane, the same chain length as the bonded phase, was employed to ensure no differential interaction between the solute and the two phases. A range of aliphatic hydrocarbons from, n-hexane to n-hexaiiiacohtane were chromatographed at two temperature 30°C and 50°C. The two temperatures were used to ensure that the retention mechanism was solely exclusion and not partition. If partition was the mechanism promoting retention, then different retention volumes... 

The LLE of twenty binary systems containing [CglTj30ClT2-Cilm][BFJ with aliphatic hydrocarbons (n-pentane, n-hexane, n-heptane, or n-octane) and aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene, or p-xylene) were presented [78]. Also, the mixtures of [CglTj30ClT2-Qlm][Tf2N]... 

Similar good results of the separation of aromatic and aliphatic hydrocarbons were recently obtained with ethyl(2-hydroxyethyl)dimethylammonium Ws(trifluoromethylsulfonyl)imide, [(Cj)2C2HOC2N][Tf2N], at 298.15 K [160]. The separation of m-xylene from n-octane by extraction with [(Ci)2C2HOC2N] [TfjN] was observed with the distribution ration of 0.3 and selectivities of range 22-31. The other ammonium salt as [(Ci)2C4HOC2N][Bp4] or 1,3-dihexyl-oxymethyl-imidazolium tetrafluoroborate was not so successful in this separation [161]. 

Hydrocarbon Benzene Iso-octane Methylcyclohexane Diisobutylene isomers Toluene n-l-Octene n-2-Octene n-Octane Vinylcyclohexene Ethylcyclohexane Xylenes... 

As an additional measure of toxicity, the hydrocarbons were diluted with the nontoxic oil to find the minimum concentration at which there was injury to Abutilon, a plant sensitive to oils. The ratings according to this evaluation agr fairly well with the previous methods. These minimum concentration studies provided little additional information other than being helpful in the valuation of some of the hydrocarbons that were not sufficiently toxic to be made selective. For example, of the hydrocarbons boiling below 280 F., the two paraffins iso-octane and n-octane were the least injurious. 

EXAMPLE 6.5 Estimation of Interfacial Tensions Using the Girifalco-Good-Fowkes Equation. The following are the interfacial tensions for the various two-phase surfaces formed by n-octane (O), water (W), and mercury (Hg) for n-octane-water, y = 50.8 mJ m 2 for n-octane-mercury, y = 375 mJ m 2 and for water-mercury, y = 426 mJ m 2. Assuming that only London forces operate between molecules of the hydrocarbon, use Equation (100) to estimate y d for water and mercury. Do the values thus obtained make sense Take y values from Table 6.1 for the interfaces with air of these liquids. 

Hydrocarbons containing two and three carbons are generally separated on packed columns. Chemically bonded materials such as n-octane or phenyl isocyanate on Porasil have proven to be good separator systems for these highly volatile nonmethane hydrocarbons. However, these systems require a separate analysis from that employed for the C4-C12 hydrocarbons (7). Recent developments include the use of capillary-type columns [e.g., Al203 porous layer open tubular (PLOT)] for separation of the lower molecular weight hydrocarbons (8). 

At low enough temperatures vibrational fine structure of aromatic chromophores may be well resolved, especially if they are embedded in a suitable matrix such as argon or N2, which is deposited on a transparent surface at 15 K. This matrix isolation spectroscopy77166 may reveal differences in spectra of conformers or, as in Fig. 23-16, of tautomers. In the latter example the IR spectra of the well-known amino-oxo and amino-hydroxy tautomers of cytosine can both be seen in the matrix isolation IR spectrum. Figure 23-16 is an IR spectrum, but at low temperatures electronic absorption spectra may display sharp vibrational structure. For example, aromatic hydrocarbons dissolved in n-heptane or n-octane and frozen often have absorption spectra, and therefore fluorescence excitation spectra, which often consist of very narrow lines. A laser can be tuned to excite only one line in the absorption spectrum. For example, in the spectrum of the carcinogen ll-methylbenz(a)anthrene in frozen octane three major transitions arise because there are three different environments for the molecule. Excitation of these lines separately yields distinctly different emission spectra.77 Likewise, in complex mixtures of different hydrocarbons emission can be excited from each one at will and can be used for estimation of amounts. Other related methods of energy-... 

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